1. Field of the Invention
The present invention relates to electrical and electronic circuits and systems. More specifically, the present invention relates to systems and methods for compressing data.
2. Description of the Related Art
Video compression is widely used in digital systems to map information rich digital video to the limited dynamic, range of conventional displays. A typical requirement is to map a 12-bit digital video signal to a display with an eight bit dynamic range. Conventionally, an input video range is divided into sections by break points. Each input section is mapped to an output display level. During the mapping transformation, some ranges of the input digital video signal may be preserved or compressed, depending on the algorithm and application. Thus, the transform may be a linear or a non-linear mapping process.
In accordance with one approach, video compression is implemented via a RAM based look up table (LUT). In accordance with this approach, the digital video data is used to address the LUT and the output thereof is range compressed display video. However, as the number of input video bits grows, the size of the LUT memory grows exponentially, as well as the effort required to update the LUT. For example, if a 12-bit input video signal is compressed into 8-bit output range, the LUT would take up (212×8)=32768-bits. For a 14 bit to 8-bit LUT, the size of memory is 4 times greater. For high-speed video systems, interfacing to external memory becomes a bottleneck and it is problematic to update the LUT. In any event, this method enables one to match any complex transfer function curve.
An alternative approach involves piecewise linear approximation. In accordance with this approach, several coarse break points are used over the input video range and linear interpolation is used between break points to map the input video to the output domain. The adjustment resolution on the shape of the input to output transfer curve relies on the number of break points used. Thus, the method cannot handle highly non-linear transfer curves resulting from complex algorithms without loss of resolution. Moreover, the method requires a high precision, fast multiplier that takes up space on a die and forces designers to use more expensive components.
Note that both methods described above use input video as an address to the LUT and the data content of the LUT contains the display video information.
Nonetheless, a need exists in the art for a system and method for data compression, particularly video data compression, that is compact in size and capable of handling complex, nonlinear compression transfer curve without compromising resolution.